Apparatus for selectively sharing the power of a multidrive unit vehicle

ABSTRACT

An apparatus for selectively sharing, towards separate users, the power of a multi-drive unit vehicle, includes a mechanical transmission, that connects propulsion units of the vehicle to at least one primary drive unit; a secondary power unit for service units, which is operatively positioned between the mechanical transmission and at least one service unit of the vehicle; as well as at least one of either a first or a second joint, that are mounted on the mechanical transmission on either side of the secondary power unit for service units and are switchable by operating suitable control means.

TECHNICAL FIELD

This invention relates to an apparatus for selectively sharing, towardsseparate users, the power of a multi-drive unit vehicle.

BACKGROUND ART

As is known, many motor vehicles of the current build type are equippedwith many services that are auxiliary and accessory to the driving ofvehicle movement, that is to say, not assigned to actual propulsion ofthe vehicle.

Some of those services also require levels of power that areconsiderable and, in the case of electric drive units, are evendifficult to supply, since the electric voltages involved are low.

Consider, for example, the vehicle air conditioning system, where themaximum power required is often greater than 3 kW; or the power steeringsystem, in which the power used is approximately 1 Kw; or even thecompressor of the brake and suspension circuit which, in large capacityvehicles may require power levels even greater than 5 Kw. Similarconditions occur for the power take offs of commercial or specialvehicles, which may use levels of power comparable to or, at times,greater than the levels of power required for driving vehicle movement.

In a traditional vehicle, all of these services draw the power necessaryfor their operation directly from the drive unit that propels thevehicle, or from an auxiliary drive unit or power supply systemdedicated specifically to the service.

In the former case, a first disadvantage is the fact that operation ofthe auxiliary services is linked to the variation in the speed(revolutions) of the drive unit that drives vehicle movement, which,varying constantly due to the variable requirements of the road route,makes the efficiency of the supply of power to secondary service unitsdependent on the instantaneous power actually and residually available.That is to say, dependent on the share of the power that is not neededfor driving vehicle movement. Another disadvantage is also the fact thatwhere the drive unit for driving vehicle movement is a combustion engineand must be kept running even if services are required while the vehicleis stationary, this results in wasted power, the production of pollutingemissions and reduced efficiency.

That is obvious, for example, in applications such as the “crane truck”type where, once the vehicle has reached the destination, use of theauxiliary service may even continue for weeks or months, during whichtime the drive unit for driving vehicle movement must be kept running inorder to supply power to the lifting system. That even applies if thepower needed is several orders of magnitude lower than the power outputthat the drive unit for driving vehicle movement is actually capable ofsupplying. Moreover, it should be noticed that this architecture ispossible, in use, only if the drive unit for driving vehicle movementcan be mechanically disconnected from the driving wheels.

In the case of a combustion engine that is easily feasible, since by itsnature the system requires a mechanical disconnection, due to the factthat the engine cannot drop below a minimum number of revolutionswithout stalling.

A very different condition is encountered in direct electric drivevehicles.

In fact, in these, the disconnection method referred to above may bedifficult to implement, meaning that an alternative solution used isthat of installing motors dedicated specifically to the individualservices.

However, whilst on one hand this solution has the advantage of removingthe link between the motor speeds, on the other hand itdisadvantageously requires an increase in the components necessary,consequently increasing: system complexity, weights, costs and overalldimensions.

With regard to that, consider for example vehicles with auxiliaryservices whose power requirements are comparable to the power needed todrive vehicle movement. These vehicles would have to be fitted with twomotors of comparable dimensions, one solely for driving vehiclemovement, the other solely for the auxiliary service. Moreover, suchvehicles would have to be equipped with other motors for additionalauxiliary services using lower levels of power.

DISCLOSURE OF INVENTION

The technical purpose of this invention is therefore to overcome suchdisadvantages. Accordingly, these results are achieved by means of anapparatus for selectively sharing, towards separate users, the power ofa multi-drive unit vehicle, made in accordance with claim 1.

The technical features of the invention, which fulfil the technicalpurpose, are clearly described in the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

The advantages of the invention are more apparent in the detaileddescription which follows, with reference to the accompanying drawingswhich illustrate an example, non-limiting embodiment of the invention,in which:

FIG. 1 is an operating block diagram schematically illustrating a motorvehicle equipped with an apparatus according to the invention;

FIG. 2 is an efficiency curve of an auxiliary service of the vehicle;

FIG. 3 is an efficiency map of a brushless electric motor with surfacemagnets advantageously usable in the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to the figures of the accompanying drawings, in FIG. 1the numeral (50) denotes a schematic diagram of a generic, multi-driveunit vehicle that comprises an apparatus (10) for selectively sharingtowards separate users (19;18) the total power that can be supplied bythe plurality of drive units (11;21).

The apparatus (10) basically comprises a mechanical transmission (12)that connects propulsion units (19) of the vehicle (50) to one or moreprimary drive units (11); and a secondary power unit (13) for serviceunits, which is operatively positioned between the mechanicaltransmission (12) and one or more service or auxiliary units (18) of thevehicle (50).

The apparatus (10) also comprises a first and a second joint (15,16),that are mounted on the mechanical transmission (12) on either side ofthe secondary power unit (13) for service units and are switchable byoperating suitable control means (20).

More particularly, said control means (20) comprise amicroprocessor-type controller (17), operatively interfaced with saidjoints (15,16), for selectively activating the sharing of power betweenthe propulsion units (19) and said one or each service unit (18),relative to operation required of the vehicle (50) at the variousmoments of its use.

The primary drive unit (11) may be a combustion engine or an electricmotor.

The secondary power unit (13) for service units comprises one or moresecondary drive units (21), which are electric motors or combustionengines, for generating power to be sent to one or more of said serviceunits (18).

The microprocessor-type controller (17) is adapted for managing thesharing of power towards the propulsion units (19) in a highly flexibleway. In fact, the sharing may be performed, for example, by givingprevalent, priority or exclusive status to requests for driving(propelling) power that come from said propulsion units (19), madenecessary by the requirements of driving the movement of the vehicle(50).

Similarly, the microprocessor-type controller (17) is adapted formanaging the sharing of power towards said one or each service unit(18), depending on a variety of different correlations resulting, forexample, between requests for driving power for the propulsion units(19) and efficiency curves (22) characteristic of said primary driveunits (11) and/or secondary drive units (21) relative to which optimummanagement can be achieved both in terms of propulsion performance, andaccessory services of the vehicle (50).

Several examples provided below give a clearer description of somefeatures and advantages of the invention.

Imagine that the primary drive unit (11), for driving vehicle movement,is an electric motor with a maximum power of 30 kW and the secondarypower unit (13) is a secondary electric motor (21), with a maximum powerof 10 kW, dedicated for example to supplying power to a refrigeratingcompressor with efficiency shown in FIG. 2 by the efficiency curve (22).

If the joint (15) is disconnected, the two electric motors (11,21) areindependent of each other and the secondary power unit (13) can supplyits power for compressor unit maximum efficiency. That is to say, itreaches 4,000 rpm, irrespective of the speed and conditions of thevehicle (50). Therefore, with this configuration, the auxiliary unit(18), that is to say, the compressor circuit, operates with maximumefficiency levels that are definitely much higher than a circuit havingthe same features that is connected directly to the transmission (12)used for driving vehicle movement, that is to say, with revolutions perminute (rpm) variable depending on the speed required of the vehicle(50) in the various propulsion conditions.

It should be noticed that with this configuration, when the vehicle isstationary, the speed of the primary drive unit (11), used for drivingvehicle movement, can be brought down to 0 (rpm), thereby interruptingall power consumption by the primary drive unit (11), since all of thepower required by the auxiliary services can be supplied by thesecondary power unit (13) for service units. Every time that operationof the refrigerating unit is not necessary (for example, after it hasreached the temperature set), the apparatus (10) will interrupt thesupply of power to the secondary power unit (13) for service units,which will be able to stop, thereby interrupting power consumption.

Therefore, in this configuration, the apparatus (10) is able to maximisethe efficiency of the auxiliary services, but not that of the systemused for driving vehicle movement.

Now imagine that the vehicle (50)—in a different example situation—istravelling at a constant speed, with a torque requirement for the driveunit that drives vehicle movement equal to 50 Nm at 2,500 rpm.Considering the drive unit efficiency map (FIG. 3, operating point 1),the drive unit for driving vehicle movement operates with 81%efficiency. In this condition, this invention allows connection of thesecondary power unit (13) for service units to the system for drivingvehicle movement. This shifts the operating point of the total driveunits driving vehicle movement to a higher efficiency value, in thisexample equal to 86%, therefore recovering 5% efficiency from the systemfor driving vehicle movement. If the service unit (18) constituted ofthe auxiliary devices does not require power, it is possible todisconnect the joint (16), so that there is no type of power draw on theservices side. Otherwise, the loss of efficiency in the case considered,due to the variation of the operating point of the system of auxiliaryservices, will be 3%.

The microprocessor-type electronic control device (17) may, therefore,manage distribution of the power of the secondary power unit's driveunit (21), dynamically evaluating the vehicle (50) requirements of powerfor driving vehicle movement and for services, the efficiency maps ofthe electric motors (11,21) and the efficiency curves or maps of theauxiliary devices, in order to always obtain from the apparatus (10)conditions allowing the vehicle (50) to operate in any condition at themaximum efficiency point achievable.

Another advantage of the invention is that it allows use of the sum ofthe powers of its drive units (11,21), either for driving vehiclemovement, or for the services. In that case, for the vehicle (50)described in the previous example and illustrated in FIG. 1, obviouslythe vehicle (50) with a 30 kW drive unit (11) for driving vehiclemovement is able to supply power up to a maximum of 40 kW either for theauxiliary services, or for driving vehicle movement.

The invention achieves the preset aims and provides further advantagesin terms of safety, since at least two drive units (11;21) are availablefor driving vehicle movement or for the services, and if one develops afault, the other can help the vehicle (50) in order to put the vehicle(50) in safer conditions.

The invention described above, which achieves the preset aims, issusceptible of evident industrial application. It may also be modifiedand adapted in several ways without thereby departing from the scope ofthe following claims. With regard to that, it should be noticed thatelectric generators may be used as alternative embodiments of theservice unit (18) and/or of the secondary power unit (13) for serviceunits. Moreover, all details of the invention may be substituted bytechnically equivalent elements.

1. An apparatus for selectively sharing, towards separate users, thepower of a multi-drive unit vehicle, which comprises a mechanicaltransmission, that connects propulsion units of the vehicle to at leastone primary drive unit; a secondary power unit for service units, whichis operatively positioned between the mechanical transmission and atleast one service unit of the vehicle; and at least one of either afirst or a second joint, that are mounted on the mechanical transmissionon either side of the secondary power unit for service units and areswitchable by operating suitable control means, said apparatus beingwherein said primary drive unit is a combustion engine or an electricmotor, said control means comprising a microprocessor-type controller,operatively interfaced with said joints, for selectively activating thesharing of power between the propulsion units and said one or eachservice unit, relative to operation required of the vehicle by its use;said microprocessor-type controller is being adapted for managing saidpower sharing towards the propulsion unit depending on priority requestsfor propelling power arriving from said propulsion units.
 2. Theapparatus according to claim 1, wherein said secondary power unit forservice units comprises at least one secondary drive unit for generatingpower to be sent to said one or each service unit.
 3. The apparatusaccording to claim 2, wherien said microprocessor-type controller isadapted for managing said power sharing towards said one or each serviceunit depending on a correlation between requests for propelling powerfrom the propulsion units and efficiency curves characteristic of saidprimary and/or secondary drive units.
 4. The apparatus according toclaim 2, wherein said one or each secondary drive unit is an electricmotor.
 5. The apparatus according to claim 2, wherein said one or eachsecondary drive unit is a combustion engine.
 6. The apparatus accordingto claim 1, wherein at least one of said joints comprises a clutch. 7.The apparatus according to claim 1, wherein said one or each unit is anelectric generator.
 8. The apparatus according to claim 1, wherein saidsecondary power unit for service units is an electric generator.